简介:Theimplantedionrange,thedepthprofileandthefilmsttuctureoftheimplantedlayerwerestudied;thecarrierconcentrationandthemobilityweremeasured;theconductivitymechanismofthefilmimplantedFeintoAl2O3ceramicwasdiscussed.TheconclusionisthattheimplantedFe2+ionsmoveintoAl2O3latticeandreplaceAl3+toformsubs-titutionimpuritiessothattheionimplantedlat-tice,ascomparedwiththeoriginalone,presentsaneffectivenegativechargewhichformsanegativechargecenter.Avacancyisboundarroundit,andanacceptorisintroducedintheforbiddenband.
简介:Ahumanfacewithcomplex3Dstructureismachinedwithamodifiedfix-lengthcompensationmethodinthispaper.ThefastdevelopmentofMEMS(MicroElectromechanicalSystems)hasstronglyenhancedtheapplicationofnewharderworkmaterials.Asalowcost,flexible,goodrepeatablemachiningprocesswithnegligibleprocessforces,micro-EDMmillingiswellsuitedforfreeformmetallicmicrostructures.Amajorprobleminmicro-EDMmillingofcomplex3Dstructureistheelectrodewear.AnewCAMsystembasedontheUGsoftwareplatformisdevelopedinordertogetgoodaccuracyandhigherefficiency.Acorrectioncoefficientisintroducedanddeducedforthemodifiedfix-lengthcompensationmethod.Usingthismethodahumanfacewithcomplex3Dstricterismachinedsuccessfullybymicro-EDMmilling.
简介:Basedonrigid-plasticfiniteelementmethod,askewrollingprocessofsteppedpartissimulated.Consideringnodesavingandeffectiveremeshing,thetetrahedronsolidelementsareusedtodiscreteworkpiece.Theworkpiecematerialadoptsrigid-plasticmodel,wheretheflowstressisfunctionofeffectivestrain,effectivestrainrateandtemperature.Thethermomechanicalcouplingisconsideredinthesimulation.Tomodelthespinningworkpieceundergoingplasticdeformation,anovelsolutionispresentedandappliedinthispaper.Thestressstateintheworkpieceandformingcharacteristicofskewrollingareanalyzed.Theformingload,includingrollertorqueandforcesinthreedirectionsarepredicted.Theaboveanalysesarehelpfultounderstandingofformingmechanismsandimprovingofprocessanddiedesign.
简介:Nearlysingle-phaseandpolycrystallinecharge-density-wavecompoundK_(0.3)MoO_3havebeenpreparedbyusingasimplemethod.Inthiswork,K_2CO_3andMoO_3wereusedasstartingmaterialsandreactedbyhotisostaticpressing(HIP)sintering.TheproductisnearlysinglephaseK_(0.3)MoO_3determinedbyX-raypowderdiffraction(XRD)andenergydispersivespectroscopy(EDS).MeasurementoftemperaturedependenceofresistivityrevealsthatthetransportpropertyofpolycrystallineK_(0.3)MoO_3obviouslydiffersfromthatofsinglecrystalduetothegrainboundariesandtheanisotropicstructureinthiskindofcompound.
简介:采用HSiCl3—NH3—N2(稀释气体)体系在石英陶瓷基板上通过低压化学气相沉积(LPCVD)法沉积出了Si3N4涂层,研究了工艺条件对涂层沉积速率的影响。结果表明,在没有稀释气体的情况下,随着沉积温度升高,Si3N4涂层的沉积速率逐渐增加,在850℃附近达到最大值,随着反应温度的进一步升高,涂层沉积速率下降。当存在稀释气体时,在所选温度范围内随着沉积温度的升高,Si3N4涂层的沉积速率一直增大,反应的表观活化能约为222kJ/mol。随着原料中NH3/HSiCl3流量比值的增大,Si3N4涂层的沉积速率逐渐增加,随后稳定,但稍有下降趋势。在所选稀释气体流量范围内,Si3N4涂层的沉积速率随着稀释气体流量的增加而增大。
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